Three college friends of the Boston Marathon bombing suspect removed a backpack with fireworks emptied of gunpowder from his dorm room three days after the attack, according to the attached FBI affidavit.

Azamat Tazhayakov and Dias Kadyrbayev are charged with conspiring to obstruct justice. A third man, Robel Phillipos, is charged with making false statements to federal investigators.

The FBI affidavit says Tazhayakov and Kadyrbayev agreed to get rid of the backpack after concluding from news reports that Dzhokhar Tsarnaev was one of the bombers.

The FBI alleges that on the night of April 18, after the FBI released photos of the bombing suspects, the three men went to Tsarnaev's dorm room. The men noticed a backpack containing fireworks, which had been opened and emptied of powder.

Kadyrbayev knew when he saw the empty fireworks that Tsarnaev was involved in the bombings and decided to remove the backpack from the room "in order to help his friend Tsarnaev avoid trouble," the FBI said in the affidavit. He also decided to remove Tsarnaev's laptop.

After the three men returned to Kadyrbayev's and Tazhayakov's apartment with the backpack and computer, they watched news reports featuring photographs of Tsarnaev. The affidavit says Kadyrbayev told authorities the three men then "collectively decided to throw the backpack and fireworks into the trash because they did not want Tsarnaev to get into trouble."

Tazhayakov and Kadyrbayev have been held in jail for more than a week on allegations they violated their student visas while attending UMass, The Associated Press reports.